For nearly two decades, how kidney cancer becomes resistant to rapalog drugs has baffled the scientific community. Now a study by researchers at UT Southwestern Medical Center s Kidney Cancer Program sheds light. Published in the Proceedings of the National Academy of Sciences, the study "Unconventional Mechanism of Action and Resistance to Rapalogs in Renal Cancer" provides evidence for an unanticipated role for nontumor cells in mediating the therapeutic effects of rapalogs in kidney cancer.